The purpose of this study is to analyze the auditory function of twins, affected and non-affected, with Alzheimers's disease. The audiologic battery is that used in the non-twin Alzheimer study of auditory function. Both affected and non-affected subjects are studied with the same battery of audiologic tests. To date eight pairs of twins of differing zygosity have been evaluated. One more known pair will be studied and then it is hoped that sufficient data will be present to determine whether there are parameters of auditory system function specific to twins (either mono- or dizygotic) and whether or not Alzheimer's disease alters or enhances these functions in a consistent way. There is no published literature in the field as of this writing.